When the industrial robot is used for work and the object is difficult to detect with accuracy, the position detecting apparatus is used for obtaining the position information of the object.
Generally, the position detecting apparatus employs an industrial camera, which requires a processing system of high computing function and often creates a problem in the manufacturing cost when in use. One method for position detection by a simplified processing system has been proposed, in which images of an object to be detected are image-formed on four photoelectric converters of 2.times.2 pcs. disposed two-dimensionally, and moved by a scanning unit slantwise of the disposal direction of the photoelectric converters so that two sets of detecting signals of the sum of outputs from two adjacent photoelectric converters are computed, whereby the one-dimensional scanning unit once scans the object to be detected so as to enable the two-dimensional position detection thereof.
Referring to FIGS. 1, 2 and 3, an object 2 to be detected lit by a light source 1 is image-formed on photoelectric converters 4a, 4b, 4c and 4d divided into four by an imaging lens 3. A galvanometer 5 as a scanning unit is disposed between the imaging lens 3 and the photoelectric converters 4a, 4b, 4c and 4d, so that the scanning signal output from a control unit 6 drives the galvanometer 5 to allow the images to move slantwise of the disposal directions of photoelectric converters 4a, 4b and 4a, 4c respectively. At first, the scanning signal is output from a driver circuit 7, the galvanometer 5 is driven, and the image of the object 2 image-formed on the photoelectric converters 4a, 4b, 4c and 4d moves slantwise in the disposal directions of photoelectric converters 4a, 4b and 4a, 4c. Detected signals P.sub.1, P.sub.2, P.sub.3 and P.sub.4 of photoelectric converters 4a, 4b, 4c and 4d are given in a computing circuit 8a and a signal .vertline.(P.sub.1 +P.sub.3)-(P.sub.2 +P.sub.4).vertline. is output therefrom. When the image of object 2 to be detected is given on the photoelectric converters 4a and 4c, the image is compared with S.sub.a preset a certain value to be S.sub.a &gt;&gt;0 and that .vertline.(P.sub.1 +P.sub.3)-(P.sub.2 +P.sub.4).vertline.&gt;S.sub.a is obtained and a gate circuit 9a outputs a signal. Next, the image of object 2 to be detected, when given to an intermediate portion between the photoelectric converters 4a to 4c and those 4b to 4d, is compared with Ta preset a certain value to be to Ta.apprxeq.0, and a signal .vertline.(P.sub.1 +P.sub.3)-(P.sub.2 +P.sub.4).vertline.&lt;Ta is obtained, so that a comparator circuit 10a outputs a signal. Signal outputs from the gate circuits 9a and comparator circuit 10a are given to an AND circuit 11a so that a sampling circuit 12a is given a sampling signal from the AND circuit 11a and reads the scanning signal of driver circuit 7 at that time to output a position signal in the direction of disposing the photoelectric converters 4a and 4b. Thereafter, when the image of the object 2 to be detected is given on the photoelectric converters 4b and 4d, signal .vertline.(P.sub.1 +P.sub.3)-(P.sub.2 +P.sub.4).vertline.&gt;Sa is obtained, thereby outputting no signal from the gate circuit 9a. Also, an input to a computing circuit 8b is output therefrom as .vertline.(P.sub.1 +P.sub.2)-(P.sub.3 +P.sub.4), the output being processed as abovementioned so that a sampling circuit 12b outputs a position signal in the direction of disposing of photoelectric converters 4a and 4c.
Thus, the position detecting apparatus such that the images formed on the four-divided photoelectric converters are moved by the scanning unit slantwise in the direction of disposing each of four-divided photoelectric converters and detecting signals thereof are computed respectively to carry out the position detection, is detectable of the two-dimensional position by use of one-dimensional scanning at a time. Such apparatus, however, requires two sets of computing circuits in parallel, becomes expensive to produce, is obtainable of a large scan width, and, when the object to be detected is different in the size, should optically change the power of image, thereby having created the problem in that the apparatus lacks in high speed response and is not detectable of two-dimensional position, such as the edge and corner, of the object to be detected.